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<h2><font color="#008000" face="Arial">Disk
Image Formats</font></h2>

<hr size="4">
<p>Disk images can be in a number
of different
formats, depending on how they were created.</p>

<p style="font-weight: bold;">DOS Order Images:</p>

<p>DOS order disk images contain the data from
each sector, stored in the same order that DOS 3.3 numbers
sectors. If you run a DOS program on the Apple which reads in
sectors one by one and then transfers them over a serial line to
the PC, you will get a DOS order disk image. </p>

<p>Apple floppy disks (normally) contain 35 tracks with
16 sectors per track, for a total of 560 sectors. Each of these
sectors contained 256 bytes of information, for a total of
143,360 bytes per disk. Therefore, DOS order disk images are
always at least 143,360 bytes long. Sometimes on the Internet you
will see a disk image that is not 143,360 bytes long; this
is probably a DOS order image with extra header information
before or after the image. In most cases, AppleWin can
automatically detect this and handle it. </p>

<p>Due to some games being incorrectly converted to a disk image AppleWin also accepts disk images of sizes:
<ul>
  <li>143,403 bytes (<i>Castle Wolfenstein</i>)</li>
  <li>143,488 bytes (<i>Rescue Raiders</i>)</li>
</ul>

<p>Some disk drives were able to handle 40+ tracks.  AppleWin accept disk images up to 40 tracks -- 163,840 bytes -- as long as the disk image is a multiple of 4,096 bytes / track.</p>

<p style="font-weight: bold;">ProDOS Order
Images: </p>

<p>ProDOS order disk images are very similar
to DOS order images, except that they contain the sectors in the
order that ProDOS numbers them. If you compress a disk with
Shrinkit on an Apple, then transfer it over a modem and
uncompress it on the PC, you will get a ProDOS order disk image. </p>

<p>Since ProDOS order disk images contain the
same information as DOS order disk images, simply in a different
order, they are also about 143,360 bytes long. When you use a
disk image of this size, AppleWin attempts to automatically
detect whether it is in DOS order or ProDOS order by examining
the contents of the disk. If the disk was formatted with a
standard operating system such as DOS or ProDOS, AppleWin will
successfully detect the format. Otherwise, it will revert to DOS
order, which is by far the most common format. To force ProDOS
order, give the file an extension of ".PO". </p>

<p style="font-weight: bold;">Nibble Images:</p>

<p>Nibble images contain all of the data on a
disk; not just the data in sectors but also the sector headers
and synchronization areas, all stored in the same encoded format
that would be recorded on a real disk's surface. At 232,960
bytes, nibble images are bigger than other images, but they can
be useful for making images of SOME copy protected software. </p>

<p style="font-weight: bold;">2mg Images:</p>

<p>2mg (or 2img) images are a wrapper around DOS, ProDOS or Nibble images.
They contain extra meta-data describing for example, DOS volume number and
write-protection.
</p>

<p style="font-weight: bold;">WOZ Images:</p>

<p>The WOZ Disk Image format is an offshoot of the <a target="_blank" href="https://applesaucefdc.com/woz">Applesauce project</a>. Capturing highly accurate bit data is of no use if you don't have a container to hold the data. The WOZ format was designed to be able to contain every possible Apple ][ disk structure and layout. It can be so accurate that even copy protected software can't tell that it isn't an original disk.
</p>

<p style="font-weight: bold;">Compressed Images :</p>

<p>All of the above can optionally be either gzip'ed or zipped. If a zip archive
contains multiple files, then AppleWin only supports using the first file. For best results
with hard disk images, uncompress first, as writing back to the image requires a full
image re-compression after every block write. Examples of typical extensions are:
<ul>
<li>.gz, .dsk.gz, .nib.gz, .2mg.gz, .woz.gz</li>
<li>.zip, .dsk.zip, .nib.zip, .2mg.zip, .woz.zip</li>
</ul>
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